1. Field of the Invention
The present invention relates to an independent rear suspension for a vehicle, such as a sport utility vehicle having a third row of seats.
2. Background Art
Independent rear wheel suspension systems generally are comprised of shock absorbers, springs and links between the frame of the vehicle and a wheel support knuckle. Upper and lower links, or control arms, generally form an articulated link that allows the vehicle to move vertically relative to the wheel. The shock absorbers and springs are generally provided to absorb impacts to the wheel and provide a smooth ride. Adjustable camber links and toe links are provided to permit adjustment of the wheel position. A stabilizer bar is generally provided to equalize forces laterally by coupling transversely aligned independent suspensions.
Suspension systems are designed to provide the desired ride and handling characteristics for a vehicle. Sports cars are generally provided with tight suspensions to improve handling. Luxury cars are provided with suspensions that are tuned to provide a softer ride with somewhat reduced handling performance. When designing or tuning a suspension system, fore and aft connections between the frame and the wheel support can be provided with softer elastomeric bushing connections to provide a softer ride. Transverse connections between the frame and the wheel support can be provided with more rigid elastomeric bushings to provide improved handling characteristics.
One rating of a vehicle suspension system is the shock ratio which is defined as the ratio of wheel travel to shock travel. A shock ratio of greater than 1.3:1 results in higher loads being applied to the frame from the shock and spring. Lower loads translate into a more comfortable ride. The length of lower control arms on full frame vehicles are limited generally to the distance between the frame rails and the wheel support knuckle. As the length of the lower control arm is reduced, the shock ratio of the suspension system increases.
The length of the lower control arm also impacts the efficiency of the stabilizer bar ratio. Stabilizer bar ratio efficiency improvements can result in the reduction of the cost and weight of the stabilizer bar.
Shock and spring location in independent rear suspensions can result in a reduction of space available for third row passenger's feet. If the shock and spring are located near the third row passenger's feet, a higher floor may be required in front of the third row seats.
The angular orientation of suspension links such as the lower control arm and toe link can impact toe-in during braking and throttle off conditions. Increasing toe-in of vehicle wheels is preferred during such conditions. Divergent toe links and lower control arms that may be required due to space limitations can reduce toe-in during braking and throttle off conditions.
Adjusting the wheel position toe-in and camber in prior art suspension systems generally must be performed in an iterative manner because, for example, in some suspension systems adjusting toe-in can cause the wheel camber to change, and visa versa. The camber must then be adjusted, which can affect the toe-in adjustment. This problem is referred to as confounding and occurs when either camber or toe-in are adjusted.
Suspension systems require adequate clearance for movement of the wheel and the suspension components relative to the vehicle frame and body. The location of suspension components can impact the design of the vehicle compartment floor pan. Suspension system components must be contained within the envelope defined below the floor pan and frame. Suspension components located forward of a seat located above the rear axle of a vehicle can result in a reduction of foot well space available in front of the seat.
It is desirable to address the above design challenges with a compact rear suspension system that provides desirable axle, suspension system and wheel clearance while affording ample space for a third row seat and foot well space. It is also desirable to provide such a suspension system that reduces confounding between toe-in and camber adjustments. The above problems and others are addressed by applicants' invention as summarized below.